0分求助，无法输出！

#include <iostream>
#include <vector>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <cstdlib>
#include <queue>
#include <stack>

#define MAX_N 1001

using namespace std;

int n;
int X1, Y1, X2, Y2;
int place[MAX_N][MAX_N];
int offset[4][2] = {{0, -1}, {1, 0}, {-1, 0}, {0, 1}};
bool visits[MAX_N][MAX_N];

struct Point
{
    int x, y;
    int time;
};

int BFS()
{
    queue<Point> q;
    Point p, t;
    p.x = X1;
    p.y = Y1;
    p.time = 0;
    visits[X1][Y1] = true;
    q.push(p);

    int x, y, tx, ty;

    while(!q.empty())
    {
        p = q.front();
        q.pop();

        x = p.x;
        y = p.y;

        if(x == X2 && y == Y2)
            return p.time;
        for(int i=0;i<4;++i)
        {
            tx = x + offset[i][0];
            ty = y + offset[i][1];

            if(tx >= 1 && tx <= n && ty >= 1 && ty <= n && visits[tx][ty] == false && place[tx][ty] == 0)
            {
                visits[tx][ty] = true;
                t.x = tx;
                t.y = ty;
                t.time = p.time+1;
                q.push(t);
            }
        }
    }

    return -1;
}

int main()
{
    //ios::sync_with_stdio(false);
    //cin.tie(0);
    //cout.tie(0);

    int i, j;

    cin>>n;

    for(i=1;i<=n;++i)
        for(j=1;j<=n;++j)
            cin>>place[i][j];

    cin>>X1>>Y1>>X2>>Y2;

    cout<<BFS()<<endl;

   return 0;
}